class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target)
    {
        unordered_map<int, int> hash;
        for(int i = 0; i < nums.size(); ++i)
            if(hash.count(target - nums[i]))
                return {hash[target - nums[i]], i};
            else hash[nums[i]] = i;
        return {};
    }
};